Characterization of xylan utilization and discovery of a new endoxylanase in Thermoanaerobacterium saccharolyticum through targeted gene deletions

Journal Article · Sun Jan 01 04:00:00 EST 2012 · Applied and Environmental Microbiology

DOI:https://doi.org/10.1128/AEM.02130-12· OSTI ID:1091628

Podkaminer, Kara K ^[1]; Guss, Adam M ^[2]; McKenzie, Heather ^[3]; Hogsett, David ^[4]; Lynd, Lee R ^[1]

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1. Thayer School of Engineering at Dartmouth
2. ORNL
3. University of California, Riverside
4. Mascoma Corporation

The economical production of fuels and commodity chemicals from lignocellulose requires the utilization of both the cellulose and hemicellulose fractions. Xylanase enzymes allow greater utilization of hemicellulose while also increasing cellulose hydrolysis. Recent metabolic engineering efforts have resulted in a strain of Thermoanaerobacterium saccharolyticum that can convert C(5) and C(6) sugars, as well as insoluble xylan, into ethanol at high yield. To better understand the process of xylan solubilization in this organism, a series of targeted deletions were constructed in the homoethanologenic T. saccharolyticum strain M0355 to characterize xylan hydrolysis and xylose utilization in this organism. While the deletion of -xylosidase xylD slowed the growth of T. saccharolyticum on birchwood xylan and led to an accumulation of short-chain xylo-oligomers, no other single deletion, including the deletion of the previously characterized endoxylanase XynA, had a phenotype distinct from that of the wild type. This result indicates a multiplicity of xylanase enzymes which facilitate xylan degradation in T. saccharolyticum. Growth on xylan was prevented only when a previously uncharacterized endoxylanase encoded by xynC was also deleted in conjunction with xynA. Sequence analysis of xynC indicates that this enzyme, a low-molecular-weight endoxylanase with homology to glycoside hydrolase family 11 enzymes, is secreted yet untethered to the cell wall. Together, these observations expand our understanding of the enzymatic basis of xylan hydrolysis by T. saccharolyticum.

• Research Organization: Oak Ridge National Laboratory (ORNL)
• Sponsoring Organization: SC USDOE - Office of Science (SC)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1091628
• Journal Information: Applied and Environmental Microbiology, Journal Name: Applied and Environmental Microbiology Journal Issue: 23 Vol. 78; ISSN 0099-2240
• Country of Publication: United States
• Language: English